What are the accuracy and inaccuracy of COVID-19 self-testing kits?

So far, many people have ordered a home self-testing kit for COVID-19 at www.covidtests.gov, and in the next few days, they may receive four free kits delivered to their homes by the U.S. Postal Service USPS. Before we receive the test kit, we will have a look at the “accuracy” and “inaccuracy” of the self-test.

One of the experts pushing for rapid testing is Dr. Michael Mina of the Harvard School of Public Health in the United States, who wrote in the New England Journal of Medicine in November 2020 that rapid testing should be promoted as early as possible as an important means of controlling the epidemic. According to modeling study predicts, promote rapid antigen detection and repeated examination and immunization, wearing masks and keep your body as may reduce the distance will be coronavirus and greatly help contain the spread of the epidemic, but because only theorized and there is no experimental and observational studies prove their effectiveness, the CDC and the FDA after early outbreak did not too much attention, And pay more attention to nucleic acid detection and vaccine development and promotion inoculation. Only recently has the potential benefits of rapid antigen testing been recognized, and the Biden administration has decided to distribute 500 million free home-based self-testing kits to Americans.

Rapid antigen detection When it comes to rapid antigen detection, people with certain medical knowledge generally agree that “speed is its advantage, but lack of sensitivity is its disadvantage”. Indeed, rapid antigen tests are generally less sensitive than nucleic acid tests. For example, testing before the onset of symptoms or later in the course of the disease when the antigen level in the sample is too low to detect would result in a negative test, whereas using the more sensitive PCR nucleic acid test could result in a positive result. In general, even with the most sensitive test (PCR nucleic acid test) and the best sample (nasopharyngeal swab), the test results cannot achieve 100% sensitivity, usually only about 80%. Antigen tests often use nasal swabs, making them even less sensitive. Rapid antigen tests tend to be only about 50 percent sensitive, the study found. Currently, there are a variety of rapid antigen test kits authorized by the FDA for emergency use. For the self-test kit that you are about to receive and use, it is often at the bottom of the sensitivity level because the operator is not a medical worker and is not familiar with the test method and other external factors.

Although the self-rapid antigen test is less sensitive than the nucleic acid test, it still plays an indispensable role in the current situation, especially in the context of the omicron pandemic. Because antigen tests tend to test positive when the virus content is high in patient samples, that is when the infectivity is high, aepeated tests can improve the reliability of test results, which is extremely effective in getting test results quickly and identifying infectious people for self-isolation. Nucleic acid testing, on the one hand, is impossible to see the results within tens of minutes like rapid antigen testing; On the other hand, due to its high sensitivity, it often remains positive after the infection period, confusing epidemic prevention and control, especially for those who need to be isolated.

What explains the results of the self-test? Antigen tests tend to be as specific as most nucleic acid tests, meaning false positives are rare. The following points should be noted for the results of self-home testing.

A positive self-test means you have the virus, you are likely infected, and should stay at home and be quarantined to reduce the risk of spreading the disease to others. Family doctors and any close contacts should also be notified.

A negative self-test means no virus has been detected and you may not be infected, but the possibility of infection cannot be ruled out. In particular, if you have a fever, cough, sore throat, runny nose, and other symptoms, you should have repeated tests or nucleic acid tests to further confirm the diagnosis.

If multiple tests are performed in a row, it is recommended that two or more tests be performed within the next few days, with at least 24 hours between tests.

Now you can see why you will receive four free tests instead of one or two, and you can see the difference between rapid antigen and nucleic acid tests and when to choose which test.

Information on COVID-19, vaccines, tests, and treatments is changing rapidly. The Internet is indeed a good source of medical information in the information explosion period, but it is more important for you to check the authenticity before you can use it for yourself.

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